Re: [regression] Bug 216856 - [ptdma] NULL pointer dereference in pt_cmd_callback during server shutdown

[Linux regression tracking #update (Thorsten Leemhuis)]

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On 30.12.22 09:27, Thorsten Leemhuis wrote:

> I noticed a bug report in bugzilla.kernel.org that looks a lot like a
> regression to my untrained eyes (it's not entirely clear). As many
> (most?) kernel developer don't keep an eye on it, I decided to forward
> it by mail. Quoting from
> https://bugzilla.kernel.org/show_bug.cgi?id=216856 :
> 
>>  Eric Pilmore 2022-12-27 22:23:50 UTC
>>
>> Observed kernel panic during host shutdown on a AMD (Milan CPU) based
>> server. The issue ended up being a NULL pointer dereference in
>> pt_cmd_callback() when
>> called from pt_issue_pending(). If you follow the flow in
>> pt_issue_pending() you will note that if pt_next_dma_desc() returns
>> NULL, then engine_is_idle will remain as TRUE, including if
>> pt_next_dma_desc() is still returning NULL in the 2nd call just prior to
>> doing the call to pt_cmd_callback().
> [...]
> #regzbot introduced: v6.1..v6.2-rc1
> https://bugzilla.kernel.org/show_bug.cgi?id=216856
> #regzbot title: ptdma: kernel panic during host shutdown
> #regzbot ignore-activity

#regzbot introduced: 6fa7e0e836e2
#regzbot monitor:
https://lore.kernel.org/all/20230210075142.58253-1-epilmore@xxxxxxxxxx/
#regzbot fix: dmaengine: ptdma: check for null desc before calling
pt_cmd_callback
#regzbot ignore-activity

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
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